Radioreceiver



Patented Nov. 12, 1929 cam ISTATES sonerrnn, or BERLIN, GERMANY}, ssmnon To GESELLSCHAFT rim DRAHT LOSE TELEGRAJHIE M. E, IL, BERLIN, GERMANY, A CORPORATION OF GERMANY RAnIonEoE vnn Application med February 24, 1925, Serial No. 11,022, and in Germany March 26, 1924.

Receiving arrangements are known in which a detector and electron tubes are used in order to avoid distortion of speech often attendant upon audion detection, and in order that greater sound intensity may be realized than is possible in simple detector reception. In these well known arrangements, the oscillations picked up by the receiving aerial are subjected to radio frequency amplification and are thereupon fed to a detector (for instance, a detector of the crystaltype). It is also usual to first demodulate the incoming high frequency energy in a detector, and to supply the resultant audio frequency to an amplifier tube thereafter, for the purpose of audio amplification.

According); to all these well known arrangements, the hookups were so chosen that the detector circuit was able to take up the energy of the incoming oscillations only when the electron tube, to which the detector circuit is connected, is operative. Therefore if the said tube should fail for some reason or another, no reception ispossible by the known methods and connections.

Now, according to the present invention, connection between the detector circuit and the electron tube arrangement is effected in such a manner that, even should an electron tube be put out of commission, primary detector reception will be possible. 1

The essential feature of the new mode 0 connection consists in that the receiving circuit, which may be the aerial itself or an oscillation circuit coupled therewith, is provided with means tending to reduce damping, while the detector directly or indirectly, is connected with this circuit in such a fashion that the'oscillations rectified by the detector are again supplied to the tube, being then heard in the telephone receiver after having been amplified.

The detector circuit in this scheme contains no discharge gap of the electron tube, but is so closed upon itself that by the insertion of the telephone, direct primary reception is rendered possible even though a tube ahead of the detector is rendered inoperative.

The above and other objects of the invention will be apparent from the following specification and claims when considered with the accompanying drawing in which:

Figs. 1 and 2 are circuits embodying different modifications of my invention.

Referring now to Fig. '1 there is coupled with theaerial circuit I and oscillation circuit II by means of coupling coils 1 and 3. The oscillation circuit II which is tuned to the incoming carrier frequency consists of coil 3 and variable condenser 2. The grid and filament of electron discharge tube 6 is connected across circuit II through condenser 13 and coil 14 fora purpose hereinafter described in detail. The plate circuit of tube 6 includes B-battery 10,

condenser 9 with telephone 8 connected in parallel, and inductance coil 7. Inductance coil 7 is variably coupled to inductance coil 3 to give regeneration.

Across a portion of coil 3 is connected the detector circuit III. The detector circuit comprises an asymmetric devicesuch as an ordinary crystal'detector 4 in series with condenser 5 across Which is connected the jack 11, for a purpose hereinafter described,

and also a coil 15 coupled to coil 14 to form the audio frequency transformer 12.

It will easily be seen that this arrangement is a reflex arrangement, the tube (Sactingfirst is ofaudio frequency transformer12 pres'enting a high impedance to radio frequencies and a low impedance to audio frequencies.

The amplified frequency is impressed on detector circuit III through coil 3 and the detected radio frequency, or, which is now audio frequency, traverses coil 15 of audio frequency transformer 12. The audio frequency is thereby impressed back upon the input circuit I of tube 6 and is amplified through the amplifying action of said tube Nil now acting as an audio frequency amplifier,

and finally heard inthe telephone 8.

It will easily be seen that, in case the tube (5 is rendered inoperative for any reason, the incoming carrier frequency will never- 'rheless be impressed upon the detector circuit III and the detected signal can be heard by inserting the telephone in jack 11.

Now, referring to Fig. 2 the antenna circuit is denoted by I and the oscillation circuit tuned to the incoming carrier frequency is denoted by H. The carrier frequency is impressed upon the grid of tube 6 through a condenser 13 connected across the coil 14 in a manner similar to that described in connection with Fig. 1.

The plate circuit of tube 6 includes B- battery 10, condenser 9 with telephone 8 connected in parallel, and inductance coil 7 va riably coupled to coil 3 to give regeneration. Connected across coil 7 is a detector circuit III comprising a detector 4 and condenser 5. Connected across the condenser 5 is a jack 11 and a coil 15 which is coupled to coil 14: to form an audio frequency transformer 12 in a manner similar to that described in connection with Fig. 1.

It will easily beunderstood that the operation of this modification is similar to the operation of the modification shown in Fig. 1. In the normal operation the arrangement acts as a one-tube reflex, the amplified radio frequency being detected and fed back into the input of the amplifier tube 6. The detected signal is again amplified and is finally heard in the telephone 8.

The fundamental difference between this arran ement and the arrangement shown in Fig. 1 is that the detector circuit is connected with the feed-back coil; instead of being directly connected with the coil 3 in the input circuit of the amplifier tube.

It will easily be understood that, should tube 6 fail for any reason, the incoming carrier frequency will be impressed directly upon detector lthrough coils 1, 3 and 7 and heard inattelephone inserted in jack 11. i

Having described several species of my invention, I am entitled to all modifications thereof as fall fairly within the spirit and scope ofthe following claims:

1. A high frequency receiving circuit comprising a three element vacuum tube, a tuned input circuit and a condenser connected in.

series with said tuned input circuit across the grid and filament of the vacuum tube, a feed back coil and a signal indicator connected in series between the plate .and' filament of the vacuum tube, an audio frequency transformer having one of the windings connected across said condenser and the other winding connected in series with a detector device and at least'a portion of said tuned input circuit and a pair of terminals connectedtoopposite ends of said last mentioned other winding.

2. In high frequency receiving circuits a three element vacuum tube, a coil and a condenser forming a tuned input circuit, a second condenser, said tuned circuit and second condenser being connected in series across the grid and filament of the vacuum tube, a feed back coil and a telephone connected in cries between the plate and filament of the vacuum tube, an audio frequency transformer having one of its windings connected acrosssaid second condenser and the other winding connected in series with a crystal detector and at least a portion of said input circuit and a pair of terminals connected to opposite ends of said last mentioned other winding.

3. Means for receiving high frequency en ergy comprising an antenna, a three element vacuum tube, and energy transferring means comprising a coupling device in said antenna, a tuned input circuit coupled thereto and a feed back coil coupled to said input circuit, a condenser connected in series with said tuned input circuit across the grid and fila- -ment of the vacuum tube, a telephone connected in series with said feed back coil betweenthe plate and filament of the vacuum tube, an audio frequency transformer having one of its windings connected across said condenser and the other winding connected in series with a crystal detector and at least a portion of said energy transferring means and a pair of terminals connected to oposi'te ends of said last mentioned other winding.

WALTER SCHAFFER. 

